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This article shows you what Camera's concept of de-interlacing is, which is concise and easy to understand, which will definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

one。 What is a field?

Before introducing the method of de-interlacing in Deinterlacer, it is necessary to mention the basics of interlacing and de-interlacing. So what is the field? the field exists in the interlaced video. Each frame of the interlaced video contains two fields, and each field contains the odd line scan line or even line scan line information of the frame picture, so it is called odd field or even field, also known as on-field or off-field. When we actually shoot, if we use the interlaced format for recording, such as pal system in SD, NTSC system, 50iMenery 60i in HD, etc., when recording the signal, they will always scan and record the next field (even field) signal, and then scan and record the upper field (odd field) signal; or vice versa. If we record the next game first, we will say it is the next game first (even number first), and vice versa, it is called play priority (odd number first). As a result, the images of the upper stage and the next field actually have a certain time displacement difference, so the images of the two scenes can not completely coincide in space, especially when shooting the active picture, the position of the active subject will often form comb stripes.

two。 Why do you need interlacing?

In the post-processing of the image, such as matting, if we directly deal with the interlaced material, it will produce edge aliasing, resulting in the decline of image quality. In addition, when interlacing digital format film and building a relatively perfect progressive video, each frame (frame) needs a high-quality picture without interlacing, so it is also necessary to de-interlacing the interlaced source video. Figure 3-schematic diagram of the parity of an interlaced image and the generation of comb stripes

three。 The common method and principle of de-interlacing is to use certain means to make the interlaced frames originally formed by interlacing no longer appear to be interlaced, and note that they are "no longer interlaced" rather than "restored". Because theoretically it is impossible to restore to 100% complete picture, in fact, the purpose of de-interlacing is to deinterlace to the maximum extent, so the two concepts are often mixed.

In general, our common de-interlacing methods are as follows:

1. Direct merging of odd and even fields

When there is no motion in the picture, the sampling information of the odd field and the even field can still be directly merged into a complete frame, as shown in the figure.

Figure 4-Odd and even fields in a still picture are directly merged into a complete frame

two。 One of the simplest solutions to field replication merging is to keep only a single field, discard another field, then copy and combine the rows in that single field into a new field, and finally merge into a frame.

Figure 5-Field copy mode reduces comb shape and brings aliasing. Although this method greatly reduces the degree of comb stripes, it also brings obvious aliasing, and the effective sharpness of the picture is greatly reduced, because only half the number of lines of picture information is used.

3. Interpolation points (applicable in most cases) in order to improve the degree of aliasing brought by the field replication mode and get relatively fast processing speed, many application software use the square method of interpolation points as the standard de-interleaving mode. This method first retains the information of a single field, then discards another field, and then creates a new scan line by interpolating points. Unlike field replication, it is smarter and creates another field by calculating the information between the rows adjacent to the field. Figure 6-interpolation points to eliminate comb shape and less aliasing

In this way, the aliasing phenomenon caused by the field replication mode is greatly reduced, and the image quality is greatly improved. However, the effective information of the picture has still been removed by half.

4. Field fusion in order to increase the effective information of the picture, we can extend the method of interpolation points, that is, we use the odd field of the original picture to get a new picture, and then use the infield point of the original even field to get another new picture, and then merge the two newly obtained pictures in half, which is the so-called field fusion method, also known as parity average merging method. Figure 7-the field fusion method retains all the information but also brings ghosting phenomenon, which can greatly reduce the abrupt aliasing phenomenon and is one of the effective methods for deinterleaving, and the effective information of the picture is expanded to full-frame picture information. However, the side effect is that the picture will be blurred due to the mixing of the two intermediate frames, and there will be ghosting in the picture with intense movement. The above content is what is Camera's concept of de-interlacing? have you learned any knowledge or skills? If you want to learn more skills or enrich your knowledge reserve, you are welcome to follow the industry information channel.

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